The Clinicopathologic Features of Inflammatory Breast Carcinoma (IBC) With Lobular Features.

Inflammatory breast carcinoma (IBC) is an aggressive form of breast cancer. Prior studies have reported the presence of lobular histology in a small percentage of tumors from patients with IBC. However, the significance of these lobular features in IBC has yet to be fully characterized. We performed a comprehensive retrospective review of patients with IBC with lobular features (IBC-LF) to evaluate their clinicopathologic features. Our IBC program registry included 524 patients over a 20-year interval, 74 (14%) of whom had lobular features. Pathology material was available for review for 28 patients, and these patients were the focus of this study. On the basis of study criteria, 12 were classified as pure invasive lobular carcinoma (ILC) and 16 as invasive carcinoma with ductal and lobular features (IDLC). All were histologic grade 2-3. Receptor profiles included ER+/HER2- in 14/28 (50%), ER-/HER2- in 7/28 (25%), and ER(+/-)/HER2- in 7/28 (25%). In the 12 cases of pure ILC, 11 showed variant morphologic features, including 6 (50%) with pleomorphic apocrine features, 3 (25%) with a solid growth pattern, 1 with signet ring-cell, and 1 with histiocytoid features. All ILC cases showed negative or aberrant staining for E-cadherin, p120, and beta-catenin on immunohistochemical studies. Dermal lymphovascular invasion was seen in 13 (46.4%) cases, while direct dermal invasion was seen in 14 (50%) cases. Our study confirms that IBC may arise from pure ILC, with negative E-cadherin expression, and usually with variant morphology. This is the first study to detail the morphologic and immunophenotypic characteristics of IBC-LF.